DOB vs. External LED Driver: Which Is Better for LED Lighting?
Why do some LED lights use a compact driver circuit on the LED board, while others use a separate external driver? The answer affects more than the size and initial cost of a light. It may also affect electrical safety, heat control, flickering, power control, dimming, and maintenance.
DOB is a design in which the LED driver circuit is placed on the same PCB as the LEDs. It is generally suitable for compact, cost-sensitive, low-power fixtures, roughly 20–25W or less, depending on the design.
The External LED Driver refers to an external power supply unit used to control the flow of electricity to the LED fixture. The LED driver is normally recommended for applications where medium and high levels of illumination are needed.
What is better
The right choice depends on the application, electrical requirements, operating environment and total cost of ownership—not simply the purchase price.
What Is DOB LED Lighting?
DOB stands for " Direct-On-Board. In the design, both the driver circuitry and LED will be mounted on the same PCB.
Since the driver is part of the LED circuit board itself, the need for an enclosure for the driver and driver connections becomes unnecessary. This results in a small package size and cost savings.
DOB is commonly considered for:
But all the LEDs and the driver are on the same board and thermal environment. The performance is affected by the circuit design, surge protection, thermal management and flicker control.
What Is an External LED Driver?
External LED drivers consist of an external power supply system that is normally designed using switched-mode power supply technology to ensure that the LEDs receive adequate regulated power.
These can be installed away from the heat created by the LEDs. The different designs of the external LED drivers will offer constant current, surge protection, and heat protection.
External drivers are commonly selected for:
Protection functions, control and dimming methods vary from one model of the LED driver to another.
DOB vs External LED Driver: Simple Comparison
Instead of a table, here is the comparison parameter by parameter.
1. Isolation and Electrical Safety:
DOB: Typically, non-isolated designs have no electrical isolation barrier between the mains supply and the LED circuit. The LED board may therefore remain at mains potential, with no SELV output.
External driver: Isolated power supplies may offer an extra-low voltage output based on the type and specifications of the power supply.
Why it matters: Electrical isolation and enclosure design are vital safety factors to consider. The safety aspect will always involve verifying electrical isolation and output.
2. Thermal Management:
DOB: The driver and LEDs share the same board and thermal environment. Where fitted, the bulk capacitor may typically operate at around 70–90°C.
External driver: The driver can be positioned away from LED heat. The supplied comparison gives a typical capacitor temperature of around 50–60°C.
Why it matters: Heat affects the longevity of electronic components, especially electrolytic capacitors. It is estimated that capacitor life decreases by half for each increase of 10°C in temperature.
3. Line Regulation:
DOB: Basic designs may show output variations as the mains voltage changes. The supplied comparison references an Indian supply range of 170–270V.
External driver: A constant-current driver typically regulates LED current within approximately =3–5%, depending on the design.
Why it matters: Stable current helps maintain consistent LED operation. Actual regulation must be checked in the product datasheet.
4. Flicker:
DOB: Simple designs having low bulk capacitance tend to result in more flicker, usually about 100Hz.
External driver: Improved filtering and current regulation lead to decreased flicker.
Why it matters: Flicker influences visual comfort and is responsible for the banding effect in cameras. Request flicker measurements in addition to the product description.
5. Power Factor and Harmonics:
DOB: The provided comparison indicates that for simple DOB circuits, the PF would be around 0.5 to 0.7, while the total harmonic distortion is usually over 80%.
External driver: With PFC built into their circuitry, drivers may achieve relatively higher PFs and lower THDs than the standard one.
Why it matters: The actual PF and THD will vary depending on design and operating conditions. Always check the technical data of the product.
6. Surge Protection:
Dob: Surge protection will be determined by the board layout and the presence of any surge protection components.
External driver: Surge protection can be obtained, depending on the model.
Why it matters: The need for surge protection arises where lighting is subjected to power disruptions. Verify the actual surge protection value and test conditions prior to purchasing.
7. Dimming:
DOB: Dimming options may be limited. Implementing interfaces such as 0–10V or DALI on a non-isolated board can raise safety and compliance concerns.
External driver: Depending on the model, support may be available for DALI, 0–10V and TRIAC dimming.
Why it matters: The driver must match the required control system. Not every external driver supports every dimming method.
8. Certification:
DOB: In case of products, the possible standards to consider include IEC 60598-1 for luminaires and IEC 62560 for self-ballasted lamps.
External driver: The comparison made from the provided information includes IEC 61347-2-13 for the LED control gear that is separate.
Why its matter: The relevant standard will be determined by the type of product and certification scope. Check the relevant certificates and reports.
9. Repairability:
DOB: The board is typically not replaceable in the field. In case of malfunction, the entire board needs to be replaced, and some designs are potted.
External driver: An external driver can usually be replaced separately if the luminaire design allows that.
Why it matters: It will affect maintenance times, repair cost, and downtime.
10. Initial Cost:
DOB: Generally lower because of its compact, integrated design.
External driver: Generally higher because the driver is a separate component.
Why it matters: Initial cost is not the only cost to consider. Other costs include energy consumption, replacement, maintenance and downtime.
11. Typical Power and Application:
DOB: Generally suited to compact, cost-sensitive fixtures of roughly 20–25W or less, subject to the design.
External driver: Usually recommended for applications exceeding about 25 W.
Why it matters: Wattage serves only as a guide and not an absolute criterion. The application itself, electrical design, heat dissipation and performance requirements should define the choice.
Constant Current vs. Constant Voltage LED Drivers
The two terms refer to different modes of powering LEDs.
Constant Current: The device controls the output current and is appropriate for use with high-power LED modules and arrays.
Constant Voltage: This type of power source delivers a stable output voltage, either 12V or 24V DC, and works best with LED strips and modules.
Important: An LED module that needs current regulation cannot be directly powered by a constant voltage source without the necessary current regulation.
Advantages
Lower initial cost
Compact size
Fewer separate components
Simple assembly
Disadvantages
Typically non-isolated in basic designs
Potentially higher flicker
Basic designs may have lower power factor
Driver and LEDs share the same thermal environment
Limited dimming options in some designs
Usually not field-repairable at board level
Actual performance depends on the design and the product's verified specifications.
DOB vs COB LED: Are They the Same?
No. DOB and COB describe different things.
DOB (Driver-on-Board) describes where the LED driver circuit is placed.
COB (Chip-on-Board) describes how LED chips are packaged on a substrate.
They are not competing technologies. A COB LED module still requires a suitable driver.
Which Should You Choose?
If minimum size and low initial cost are most important, particularly for an appropriate low power enclosed fixture, select DOB.
For applications where electrical isolation, thermal control, current regulation, surge protection, reduced flicker, dimming or on-site replacement are more important, opt for an external LED driver.
For industrial use, outdoor use and long hours, an external driver is often more convenient as a starting point; however, the specific device should still meet the criteria for the application.
Conduct a TCO comparison.
Compare Total Cost of Ownership
Do not compare drivers on purchase price alone.
Total Cost of Ownership (TCO) = Initial Cost + Energy Cost + Maintenance Cost + Replacement Cost + Downtime Cost
The better choice is the one that meets the technical requirements while delivering the most suitable overall cost over the intended service period.
Why Consider Pyrotech for LED Lighting?
Pyrotech Technologies manufactures LED lighting products and has in-house LED driver capability. When evaluating a Pyrotech lighting solution, consider the driver type, power rating, electrical isolation, current regulation, surge protection, flicker performance, thermal conditions and maintenance requirements for the specific model.
For an informed comparison, review the relevant product datasheets, test reports and certification documents rather than relying on the driver category alone.
Frequently Asked Questions (FAQs)
1. What is the difference between DOB and an external LED driver?
DOB integrates the driver circuit and LEDs on the same PCB. An external LED driver is an independent power supply designed to control power to the LED module and can provide extra isolation, protection, dimming and replacement options.
2. Which is better for industrial LED lighting?
An external LED driver is generally preferred for industrial, outdoor, medium- and high-power applications because of the potential benefits in thermal management, regulation, protection and serviceability. The specific driver's ratings must still be verified.
3. Is DOB suitable for low-power LED lights?
In compact and cost-sensitive applications with a fixture of approximately 20-25W or less, DOB can be considered for the following reasons: circuit design, thermal management, flicker control and safety
4. What is the difference between a constant-current and constant-voltage driver?
A constant-current driver is used to control the output current to a compatible LED module. A constant-voltage supply is designed to supply a fixed voltage, typically available in two ways: 12V or 24V DC.
5. Does COB mean the same as DOB?
No. COB describes the packaging arrangement of LED chips, while DOB describes the placement of the driver circuit. A COB LED module still requires a suitable driver.
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